NSC94-EPA-Z-008-004

Figure 4.6 25-TiMCM-41 Isothermal Plot............................................................................... 29Figure 4.7 75-TiMCM-41 IsothermPlot................................................................................... 30Figure 4.8 BET Surface Area v. s. Ti/Si Mole Ratio................................................................ 31Figure 4.9 Pore arrangement diagram, Marler et al., 1996. ..................................................... 31Figure 4.10 DTA plot of 50-TiMCM-41. ................................................................................. 32Figure 4.11 FTIR Spectra of TiMCM-41 (A) After calcination, (B) Before calcination......... 33Figure 4.12 FTIR spectra of (A) silicious MCM-41, (B) 50-TiMCM-41................................ 33Figure 4.13 UV-vis spectra of various TiMCM-41 and TiO 2 ................................................... 34Figure 4.14 Schematic model showing apparent "lamellar structure" from a projection of ahexagonal array tubules, (Chenit, et al., 1995)........................................................... 34Figure 4.15 TEM image of 50-TiMCM-41 (30000x) .............................................................. 35Figure 4.16 The XRD patterns of InVO 4 prepared with various amount of NiO loading. (A)InVO 4 , (B) 0.5wt% NiO/InVO 4 , (C) 1.0wt% NiO/InVO 4. ......................................... 38Figure 4.17 The SEM micrographs of InVO4 prepared with various amount of NiO loading.(A) InVO 4 , (B) 0.5 wt% NiO/InVO 4 , (C) 1.0 wt% NiO/InVO 4 ................................. 39Figure 4.18 The wavelength-current spectra of 500W halogen lamp, incident light powerprobed near reactor was about 143 μW/cm 2 for λ is from 300 to 900 nm. ................ 40Figure 4.19 The SEM-EDS spectra of InVO 4 loaded with 0.5 wt% NiO. ............................... 41Figure 4.20 The SEM-EDS spectra of InVO 4 loaded with 1.0 wt% NiO. ............................... 41Figure 4.21 The UV-Vis spectrum of InVO 4 prepared with various amount of NiO loading. (A)InVO 4 , (B) 0.5 wt% NiO/InVO 4 , (C) 1.0 wt% NiO/InVO 4 . ...................................... 42Figure 4.22 Dependence of the photocatalytic activity for carbon dioxide over NiO/InVO 4upon the amount of NiO loading; under visible light irradiation. Catalyst: 0.14g;0.2N KHCO 3 aqueous solution; 50ml........................................................................ 43Figure 4.23 The XRD patterns of InVO 4 prepared with pretreatment on various amount ofNiO loading. (A) InVO 4 , (B) 0.5wt% NiO/InVO 4 R500-O200, (C) 1.0wt%NiO/InVO 4 R500-O200 . ............................................................................................. 46VIII

Figure 4.24 The SEM micrographs of InVO 4 prepared with pretreatment on various amount ofNiO loading. (A) InVO 4 , (B) 0.5 wt% NiO/InVO 4 R500-O200, (C) 1.0 wt%NiO/InVO 4 R500-O200.............................................................................................. 47Figure 4.25 The UV-Vis spectra of InVO 4 prepared with pretreatment on various amount ofNiO loading. (A) InVO 4 , (B) 0.5 wt% NiO/InVO 4 R500-O200, (C) 1.0 wt%NiO/InVO 4 R500-O200.............................................................................................. 49Figure 4.26 Dependence of the photocatalytic activity for carbon dioxide over NiO/InVO 4upon the amount of NiO loading; under visible light irradiation. Catalyst: 0.14g;0.2N KHCO 3 aqueous solution; 50ml........................................................................ 50IX

List of TablesTable 2.1 The comparison of pore size and structure of the catalyst......................................... 5Table 2.2 The methanol yield and quantum efficiency of catalysts......................................... 11Table 2-3 Expected mesophase sequence as a function of the packing parameter (Israelachviliet al., 1976)............................................................................................................... 13Table 4.1 N 2 Sorption Data of TiMCM-41............................................................................... 30Table 4.2 Wall thickness of TiMCM-41................................................................................... 32Table 4.3 The nominal and actual loading of NiO on InVO 4 samples..................................... 42Table 4.4 Band gap of InVO4 serious ...................................................................................... 43Table 4.5 Band gap of InVO4 serious with pretreatment......................................................... 49X

Chapter1. IntroductionGreenhouse gases such as CO 2 , CH 4 and CFCs are the primary causes of global warming.The atmospheric concentration of CO 2 has increased due to human activity. At present in theearth, burning the hydrocarbon fuel is the main source of energy, so the atmosphericconcentration ratio of CO 2 is much higher than the past. Besides looking for a clean and moreefficient energy is the important issue, finding the way for CO 2 reduction is another purpose.The main products of the photocatalytic reduction of CO 2 and H 2 O are CH 3 OH and CH 4 ,as well as trace amounts of CO, C 2 H 4 and C 2 H 6 . Because methane is a kind of gas and hard tocollect, methanol is one species of liquid and is easy to obtain, our aim to get highconcentration of CH 3 OH from photocatalytic reduction.1

Chapter2. Literature Review2.1 Catalyst Systems for Methanol FormationAnpo did a series of researches on Ti-zeolite and Ti-mesoporous materials from 1997. Thespecies of photocatalysts are numerous, including Ti-oxide/Y-zoelite, Ti-MCM-41,Ti-MCM-48, FSM-16, Ti-β zeolite, and Self-standing porous silica thin films, etc.In 1997, Anpo used an ion-exchange method with an aqueous titanium ammonium oxalatesolution using Y-zeolite examples (SiO 2 /Al 2 O 3 =5.5) to get the highly dispersed titaniumoxides included within zeolite cavities.[1] The photocatalytic reaction was carried out with thecatalysts in a quartz cell. First, the catalysts were degassed at 725K for 2 h, heated in O 2 at725 K for 2 h, and finally evacuated at 475K to 10 -6 Torr for 1 h. Then using a 75 Whigh-pressure Hg lamp (λ > 280nm) for UV irradiation in the presence of CO 2 (24μmol, 5.5Torr) and gaseous H 2 O (120μmol) at 328K.UV irradiation of the powdered TiO 2 and the Ti-oxide/Y-zeolite catalysts prepared byion-exchange or impregnation methods in the presence of a mixture of CO 2 and H 2 O led tothe evolution of CH 4 and CH 3 OH in the gas phase at 328 K, as well as trace amounts of CO,C 2 H 4 , and C 2 H 6 .Figure 2.1 Products distribution of the photocatalytic reduction of CO 2 with H 2 O on (a) theanatase TiO 2 power, (b) imp-Ti-oxide/Y-zeolite (10.0%), (c) imp-Ti-oxide/Y-zeolite (1.0w%),(d) ex-Ti-oxide/Y-zeolite and (e) Pt-loaded ex-Ti-oxide/Y-zeolite (10wt%) catalysts.Figure 2.1 shows the reactivity of CH 4 and CH 3 OH formation, and it also exhibits thelevel of photocatalytic reactivity depending on the type of titanium oxide catalysts. Thehighest efficient catalyst for formation of methanol is the ex-Ti-oxide/Y-zeolite catalysts, andthe highest efficient catalyst for formation of methane is the Pt-loaded ex-Ti-oxide/Y-zeolite(10wt%) catalysts.From Figure 2.2, one can see a blue shift in the absorption band of titanium oxide which2

can attribute to the size quantization effect due to the presence of extremely small Ti-oxideparticles and/or the presence of highly unsaturated Ti-oxide species having a tetrahedralcoordination.Figure 2.2 Diffuse reflectance absorption spectra of (a) the anatase TiO 2 powder, (b) theimp-Ti-oxide/Y-zeolite (10.0 wt % as TiO 2 ), (c) the imp-Ti-oxide/Y-zeolite (1.0 wt % asTiO 2 ), (d) the ex-Ti-oxide/Y-zeolite, and (e) the Pt-loaded ex-Ti-oxide/Y-zeolite catalysts.Methanol formation depends on the highly dispersed isolated tetrahedral TiO x species,like the ion-exchanged TiO x /Y-zeolite catalysts. Adding Pt increased methane formation.In 1998, Anpo reported the reaction results on Ti-mesoporous zeolites, and Pt-loadedTi-MCM-48. It is clear that the photocatalytic reaction rate and selectivity for the formation ofCH 3 OH strongly depend on the type of the catalyst.Figure 2.3 The yields of CH 4 and CH 3 OH in the photocatalytic reduction of CO 2 with H 2 O on(a) TiO 2 powder, (b) TS-1, (c) Ti-MCM-41, and (d) Ti-MCM-48 zeolite catalysts.3

In order to know exactly the influence of adding Pt onto the Ti-MCM-48 catalysts, Anpoalso did some research. Figures 4 and 5 show the result of the Ti-MCM-48 catalyst comparingwith the Pt-loading onto the Ti-MCM-48 catalysts. Although the addition of Pt onto theTi-MCM-48 is effective in increasing the photocatalytic activity, only the formation of CH 4 ispromoted, accompanied by a decrease in the CH 3 OH yield.Figure 2.4 The effects on Pt-loading on the yields of CH 4 and CH 3 OH in the photocatalyticreduction of CO 2 with H 2 O on the Ti-MCM-48 zeolite catalyst. (a) Ti-MCM-48, (b)Pt-loadedTi-MCM-48(0.1 wt% as Pt), and (c)Pt-loaded Ti-MCM-48 (1.0 wt% as Pt).Figure 2.5 The yields of CH 4 and CH 3 OH in the photocatalytic reduction of CO 2 with H 2 O on(a) TiO 2 powder, (b) TS-1, (c) Ti-MCM-41, (d) Ti-MCM-48, (e) the Pt-loaded Ti-MCM-48catalysts.4

Table 2.1 The comparison of pore size and structure of the catalyst.Catalyst Pore StructuresizeTS-1 ca. 5.7Åthree-dimensional channelstructureTi-MCM-41 >20 Å one-dimensional channel structureTi-MCM-48 >20 Å three-dimensional channelsBesides the higher dispersion state of the titanium oxide species, other distinguishingfeatures of these zeolite catalysts are: TS-1 has a smaller pore size (ca. 5.7 Å) and athree-dimensional channel structure; Ti-MCM-41 has a large pore size (>20 Å) but aone-dimensional channel structure; and Ti-MCM-48 has both large pore size (>20 Å) andthree-dimensional channels. Ti-MCM-48 zeolite than with any other catalysts used here maybe a combined contribution of the high dispersion state of the titanium oxide species and largepore size having a three dimensional channel structure.In 1999, Anpo reported the mesoporous cavities of the FSM-16 zeolite(Ti-oxide/FSM-16) by a CVD method. The selectivity of CH 3 OH formation was found tobecome higher when the degassing temperature of FSM-16 is increased.Figure 2.6 The diffuse reflectance spectra of (a)Ti-oxide/FSM-16, (b)Ti-oxide/FSM-16, (c)Ti-oxide/FSM-16, (d)Ti-oxide/FSM-16, and(e)anatase TiO 2 powder as a reference as well as the Photoluminescence spectrum of theTi-oxide/FSM-16 and the effect of the addition of CO 2 or H 2 O on the spectrum. (A) 0,(B) CO 2 ; 1.0 Torr, (c) H 2 O; 1.0 Torr, (D) H 2 O; 5.0 Torr. (UV diffuse reflectance spectra weremeasured at 295K. Photoluminescence spectrum was measured at 77K. Excitation wavelengthwas 280nm±5nm).In 2001, Anpo found that Ti/FSM-16 photocatalytsts prepared by various methods would5

exhibit different structures and reactivity for the photocatalytic reduction of CO 2 and H 2 O.Ti-FSM-16 photocatalysts (Ti contents: 1%) were synthesized by four preparation methods,discriminated from (1) TiO2/FSM-16, (2) imp-Ti/FSM-16, (3) anc-Ti/FSM-16, (4)Ti/FSM-16.Figure 2.7 XAFS spectra of the Ti/FSM-16 photocatalysts prepared by various methods. Ticontent: 1 wt%. N: Coordination number. R: Ti-O bond distances (Å).In the XAFS spectra, Ti/FSM-16 and anc-Ti/FSM-16 showed an intense single pre-edgepeak which indicates that the Ti-oxide species of this photocatalysts exists in tetrahedralcoordination. The imp-Ti/FSM-16 and TiO2/FSM-16 exhibited a weak pre-edge, and thismeans there were octahedrally coordinated Ti-oxide on these photocatalysts.According to the EXAFS (FT-EXAFS) spectra of the photocatalysts, Ti-FSM-16 andanc-Ti/FSM-16 exhibited only Ti-O peaks, pointed out the isolated Ti-oxide species on thesephotocatalysts. For imp-Ti/FSM-16 and TiO2/FSM-16, an intense peak around 2.7Å as wellas Ti-O peak assigned to the neighboring Ti atoms (Ti-O-Ti).Through UV irradiation of these four photocatalysts, anc-Ti/FSM-16 and Ti-FSM-16with a highly dispersion of tetrahedrally coordinated Ti-oxide species showed highphotocatalytic reactivity and high yield of CH 3 OH formation.Ti-β zeolite is one of Anpo’s research. There are two types of Ti-β zeolites usinghydrothermal synthesis under different conditions using OH- and F- ion as anions of thestructure-directing agents (SDA). It was found that the Ti-β zeolites using OH- ions (Ti-β6

(OH)) showed hydrophilic properties, and the Ti-β zeolites using F- ions (Ti-β(F)) exhibitedhydrophobic properties.Figure 2.8 Yields of the products formed in the photocatalytic reduction of CO 2 with H 2 O andpholuminescence of various Ti/FSM-16 photocatalysts.Figure 2.9 H 2 O adsorption isotherms at 298 K of (a) Ti-β(OH), (b) TS-1, and (c) Ti-β(F)catalysts.Figure 2.10 Yields of CH 4 and CH 3 OH in the photocatalytic reduction of CO 2 with H 2 O at323 K on the Ti-β (OH), TS-1, Ti-β (F), and TiO 2 (P-25) catalysts. Intensity of light is 265μW cm -2 . Reaction time is 6 h.7

The different properties in H 2 O affinity to the zeolite surface let to a strong influence onthe reactivity and selectivity for the photocatalytic reduction of CO 2 and H 2 O.Ti-β (OH) exhibits higher reactivity compared to Ti-β (F). On the other hand, theselectivity for the formation of CH 3 OH from Ti-β (F) (41%) is higher than for that from Ti-β(OH) (11%). Moreover, the selectivity for the formation of CH 3 OH from Ti-β (F) is higherthan that of the other Ti-containing zeolites and molecular sieve catalysts (TS-1 (23%),Ti-MCM-41 (31%), Ti-MCM-48 (29%)).Ti-β (OH) catalyst having hydrophilic properties exhibited higher reactivity than Ti-β (F),attributed to the higher concentration of the charge-transfer excited complexes, (Ti 3+ -O - )*.On the other hand, a highly selectivity for the formation of CH 3 OH was observed on the Ti-β(F) catalyst having hydrophobic properties. Therefore, the hydrophilic-hydrophobic propertiesof these zeolites were found to be the controlling factor in the reactivity and selectivity for thephotocatalytic reduction of CO 2 with H 2 O.In 2002, the transparent Ti-containing mesoporous silica thin film is applied to thephotocatalystic reduction of CO 2 and H 2 O. It was synthesized by the solvent evaporationmethod from TMOS, VTMOS, TIP, and C 18 TAC. When the water/Si ratio was 1/3 and 4/3,they are referred to as Ti-PS-h-x and Ti-PS-c-x. (x is the Si/Ti ratio, i.e. 25 or 50; h refer tohexagonal, c refer to cubic)Figure 2-11. Yields of CH 4 and CH 3 OH in the photocatalytic reduction of CO 2 with H 2 O on(a) Ti-PS(h, 25), (b) Ti-PS(c, 50), (c) Ti-MCM-41, the powdered form of (d) Ti-PS(h, 50) and(e) Ti-PS(h, 50). Reaction time is 6 h and intensity of light is 265μW cm -2 .8

Table 2.2 The methanol yield and quantum efficiency of catalystsIn this work, the synthesis of Ti/HY materials, and characterization of the catalysts byXRD, UV-visible and SEM were investigated. The materials were tested for CO 2 reactingwith H 2 O to form methanol.2.2 Ti-MCM-41In 1992 theresearchers at Mobil Oil Corporation in British reported a new family ofcrystalline mesoporous molecular sieves called M41S family, (Kresge, et al. 1992, Beck, et al.1992.) including MCM-41 (hexagonal phase), MCM-22, MCM-48 (cubic phase) and MCM-L(lamellar phase). (Huo et al., 1994(a). Huo et al., 1994(b)). This attracted the attentions ofmany scientists working in areas such as the zeolites and related materials, since it process ahexagonal array of uniform pores and exhibits high surface area (typically > 800 m 2 /g), andhigh hydrocarbon sorption capacities (>0.7 m 3 /g) (Gontier; Tuel, 1995). Figure 2.16 shows theMCM-41 structure with hexagonal pore array. Many excellent reviews have been reported(Sayari, 1996; Raman et al., 1996; Abdelhamid, 1996.). The first approach of hydrothermalsynthesis used alkyltriethyl-ammonium surfactant as a template, mixing with acid sodiumsilicate solution and reacted in a Teflon stainless-steel autoclave at 100 ℃ for 144 h. Thestructure of the mesophase depends on the compositions of the mixture, the pH value, and thetemperature (Huo et al., 1994(b)). Typically, uniform mesopores with the diameter in the rangof 5-10 nm could be obtained by using C n H 2n+1 N + (CH 3 ) 3 as a template, where 8 < n < 16. Size,charge, and shape of surfactants are important structure-determining parameters of theMCM-41. A local effective surfactant critical packing parameter is described in terms of CPP=V H /a0l c , where V H is the hydrophobic portion of surfactant molecular, a0 is the effectivehead group area at micelle surface, l c is the critical length of the hydrophobic tail, which istypically : l c ≦ 1.5 + 1.265 noA , where n is the carbon number in the chain. The expectedesophase sequence as a function of the packing parameter is shown in Table 1-1. (Israelachviliet al., 1976).11

Figure 2.16 MCM-41 structure with hexagonal pore array (Beherns P.; Stucky G. D., 1993)Beck et al. (1992) proposed that these materials were formed via a liquid crystalmechanism in which surfactant serves as organic templates. Figure 2.17 is the synthesismechanism proposed by Beck. Chen et al., (1993) used NMR technology and found that eventhe concentration of quarternary ammonium was not high enough to form hexagonal liquidcrystal, mingled silicate into the solution still made uniform hexagonal array. Figure 2.18 isthe synthesis mechanism proposed by Chen et al. Minnier et al. (1993) proposed anothermechanism. The gradual growth between the surfactant C 16 TMABr and silicate species wasobserved by XRD. They discovered that lamellar phase would form first before hexagonalphase as a transition state, as presented in Figure 2.19. The driving force for the lamellarphase transferred to hexagonal phase is ascribed to the charge imbalance which is associatedwith the condensation of silicate species. It made the rearrangement of the silicate structurehappened and became hexagonal arrays structure eventually. At present there is a broadconsensus that the formation of M41S materials can be basically described in a three-stepprocess (Figure 2.20). The first step, driven by electrostatic interactions, ion pairs formedbetween silicate and surfactant. The ion pairs then self-organized into a mesophase. The laststep is the condensation of the inorganic species leading to a grid structure (Firouzi et al.,1995). A different structure with tubules-within-a-tubules hierarchical order of MCM-41 wasstudied by Lin et al. (1996). The transformation is lamellar → ripple → tubular, aspresented in Figure 2.20. They found that the silicate-surfactant system is close to thelamellar-hexagonal phase boundary under high pH.12

Table 2-3 Expected mesophase sequence as a function of the packing parameter (Israelachviliet al., 1976).CPPTypes of surfactants ExpectedAggregate structure< 0.33 Single chain, relatively Spherical or ellipsoidallarge headsmicelles0.33-0.5 Simple surfactants with Relatively large cylindricalrelatively small head group;or rod-shaped micellesionics with high electrolyteconcentration0.5-1.0 Double chains with large Vesicles or bilayerheadsstructuresFigure 2.17 The synthesis mechanism proposed by Beck et al., 1993.13

Figure 2.18 The synthesis mechanism proposed by Chen et al., 1993.Figure 2.19 The synthesis mechanism proposed by Monnier et al., 1993.14

Figure 2.20 The synthesis mechanism proposed by Firouzi et al., 1995.A little acidification results in a mixed lamellar-hexagonal phase in which layers ofhexgonally arrange rod-like micelles are separated by bilayers of surfactants and water(Figure 2.20A). Further acidification leads to the condensation of silicates and chargeimbalance on membrane surface, favoring the curvature of the membrane along only ondirection (Figure 2.20B) because of the intrinsically anisotropic membrane layers. Finally,neutralization will then bend the membrane completely into tubules (Figure 2.20C). Thedriving force arises from the imbalance charge at the surface which is associated with thecondensation reaction of the silicate-oxygen bond as the pH is lowered.Due to the inactive property of the MCM-41 synthesized with only pure silicon, Al, Ti,V, Sb, Fe, Pd, (Huo et al., 1994(a). Corma et al., 1994(a)) or Ga (Cheng et al., 1996) was usedto take place of the silicon position and became the active site in MCM-41. Substitution of Tiis particularly interesting because of the success of Ti-substituted zeolites in oxidation ofvarious organic substrates. TS-1 and TS-2 with MFI and MEL structures respectively wereshown to be active and selective catalysts for oxidation of phenol to catechol andhydroquinone (Reddy et al. 1990; Thangaraj et al., 1991). The synthesis of the large-porezeolite Ti-Beta with channels about 0.7 nm was reported. (Camblor et al., 1992; Camblor etal., 1993). It was able to oxidize cycloalkanes, cyclohexenes, and cycloalcohols moreefficiently than TS-1 zeolite (Blasco et al., 1993, Corma et al., 1994(b)). Using Ti zeolites asselective oxidation catalysts of fine chemicals, there was a need for producing molecular sieve15

catalysts with pore diameters larger than 0.7 nm Corma et al., (1994(c)) synthesizedTiMCM-41 successfully, this material possessed pore diameters in 2.8 - 3.5 nm and Ticontents up to 2.2 wt %.Figure 2.21 The synthesis mechanism proposed by Lin et al., 1997.It is known that incorporation of transition metal cations in the framework of pure silicapolymorphs of zeolites is not always easy and usually limited to less than 3 wt % (Corma etal., 1994(c)). One of the reason is that these cations have a radius larger than Si 4+ , and theirincorporation in a zeolite framework distorts the latter. Therefore, the zeolite can onlycrystallize within a small metal concentration. Spectroscopic characterization showed Ti 4+ions where isolated in silica domains only for very low Ti contents (< 2 wt%). For highercontents, UV-visible spectroscopy revealed the presence of partially polymerized Ti species,Corma et al. (1994(d)) prepared TiMCM-41 containing 2.2 wt% Ti and concluded that Tiatoms were isolated and tetrahedrally coordinated.Although the thin wall (about 1nm) might be the main cause of the limited stability,MCM-41 is thermally stable under an inert atomsphere below 1273℃ (Rhee et al., 1996).Ryoo et al. (1996) claimed that the structure of MCM-41 was lost completely upon boiling inwater for 2 days due to hydrolysis of silicate. The stability of TiMCM-41 was found to be lowcompared to pure-silicious MCM-41, the substitution of Ti for Si in the silica framework ofMCM-41 greatly reduce the stability of the structure (Koyano et al., 1997).16

In this work, the synthesis of TiMCM-41 materials, and characterization of the catalystsby XRD, FTIR, UV-visible, DTA, TEM, and nitrogen sorption were investigated. Thematerials were tested for CO 2 reacting with H 2 O to form methanol.17

Chapter3. Experimental3.1 Chemicals3.1.1 UV light(1) Sodium silicate powder (Showa), approx. SiO 2 : 50 ~ 55 %, Na 2 O : 23 ~ 27 %(2) Hexadecyltrimethylammonium bromide, C 16 TMABr , 99.9 % (TCI Tokyo Kasei)(3) Titanium (IV)-isopropoxide, (C 3 H 7 O) 4 Ti, 98 % (ACROS, USA)(4) Titaniumchloride, TiCl 4, 99.9 % (TCI Tokyo Kasei)(5) H 2 SO 4 , 97 % (Hayashi)(6) Type Y molecular sieve, hydrogen form (Strem Chemicals, Inc.)3.1.2 Visible light(1) Indium (III) oxide (In 2 O 3 , 99.5%)(2) Vanadium (V) oxide (V 2 O 5 , 99%)(3) Nickel (II) nitrate hexahydrate (Ni(NO 3 ) 2 , 99.0%) (purchased from Merck Chemical)(4) Niobium (V)oxide (Nb 2 O 5 ,>99.9%) (Fluka Pure Chemical (Switzerland))(5) Tantalum (V) oxide (Ta 2 O 5 , 99.99%) (Aldrich Chemicals (MO, USA))(6) Nickel (II) oxide (NiO, 99.99%), with a purity of 99.99%(Sigma-Aldrich Chemicals)3.2 Preparetion of ultra violet catalysts3.2.1 Synthesis of Ti/HYA. Pretreatment HY-Zeolite:NH 4+ Y-zeolite was calcined at 500℃ for 5 h to obtain HY.B. Impregnationsupport:HY-zeoliteTi salt: TiOSO4(Titanium(Ⅳ) Oxysulfate, 99.99%)C. Preparation of 10 wt.% Ti/Y-zeolitea. Take 5g HY-zeoliteb. Take 1.2274ml TiOSO4 loaded in 5 ml distilled waterc. Added sample b into a and mixed them,d. calcined the sample c at 400℃ for 3 h.3.2.2 Synthesis of TiMCM-41TiMCM-41 was synthesized according to the procedure reported by Lin et al. (1996).Several samples with various Si/Ti molar ratios were synthesized. The synthesis procedure isshown in Figure 3.1. The synthesizing reactions were carried out in a Teflon-linedstainless-steel autoclave as shown in Figure 3.2. The procedure was as following: Twoaqueous solutions were made by dissolving 9.1g organic template C 16 TMABr in 15 ml purewater with stirring 10 min and 5.76 g sodium silicate in 10ml pure water with stirring 10 min.When solutions were both homogenized, added them together with the solution which mixed18

y (C 4 H 7 O) 4 Ti and H 2 O 2. The three solutions were mixed completely. The pH value wasadjusted about 10 with 2.0 M H 2 SO 4. The final mixture was poured into a Teflon-linedstainless-steel autoclave at 100 °C for reaction for 48 hours. The reaction products werefiltered, washed with distilled water and dried in air at 100 °C overnight. Finally the driedproducts were calcined at 540 °C for 6 hours at a rate of 75 °C/h. The products were denotedas n-TiMCM-41 where n represents Si/Ti molar ratio of the samples.3.2.3 Preparation Ti/MCM-41and Ti/HYTi/MCM-41 and Ti/HY zeolite were prepared by impregnating aqueous solution of TiCl 4into MCM-41 and NaY zeloit. The loading of Ti was 3.13 wt%. The samples were dried in theoven over night and calcined at 540 °C for 6 h at a rate of 75 °C/h.3.3 Preparation of visible light catalysts3.3.1 Preparation of InVO 4Preparation of indium-vanadium oxide has been referred to Ye’s method (2002). Thepolycrystalline samples of InVO 4 were synthesized by a solid-state reaction method. Thepre-dried In 2 O 3 and V 2 O 5 were used as starting materials. The stoichiometric amounts ofprecursors were mixed and reacted in an aluminum crucible in air at 850℃ for 12 h.3.3.2 Loading Nickel oxide on InVO 4 : NiO/InVO 4The polycrystalline samples of InVO 4 were synthesized by a solid-state reaction method.The pre-dried In 2 O 3 and V 2 O 5 were used as starting materials. The stoichiometric amounts ofprecursors were mixed and reacted in an aluminum crucible in air at 850 o C for 12 h. In orderto obtain high photocatalytic activity, it is essential to load a metal or metal oxide on thesurface of photocatalyst as electron acceptors. We tested loading NiOx on surface of thecatalyst. NiO co-catalysts were loaded by incipit wetness impregnation from Ni(NO 3 ) 2 . The1.0 wt.% nickel was loaded on surface of the catalysts powders from aqueous Ni(NO 3 ) 2solution. The Ni-loaded photocatalysts were calcined at 350℃ for 1 h in air. The detailedpreparation method is shown in Figure 3.1.3.3.3 Different amount of NiO loadingWe tested loading NiOx on surface of the catalyst. The 0.5, 1.0 wt.% nickel oxide wasloaded on surface of the catalysts powders from aqueous Ni(NO 3 ) 2 solution, respectively. Theflow chart is shown in Figure 3.43.3.4 Pretreatment on different amount of NiO loadingThe Ni-loaded photocatalysts were prepared by H 2 (pressure: 0.3 M Pa, flow rate: 25cc/min) reduction at 500 O C for 2 h and subsequent O 2 (pressure: 0.15 M Pa, flow rate: 25cc/min) oxidation at 200 O C for 1 h. The double-layered structure of metallic Ni and NiO wasformed on the surface of photocatalyst by this reduction–oxidation procedure. The flow chartis shown in Figure 3.5.19

3.4 Characterization(1) X-ray Diffraction (XRD)The XRD experiments were preformed using a Siemens D-500 powder diffractometerwith Cu-Kα radiation (40 kV, 30 mA), 0.02° step size and 1 second step time from 1° to 8°(2) N 2 sorption measurementN 2 sorption isotherms were measured at -196.15 ℃ using a Micromeritics ASAP-2000.Prior to the experiment, samples were dehydrated at 350 °C until the vacuum pressure wasbelow 8 mmHg.(3) Differential Thermal Analysis (DTA)DTA was carried at using Perkin-Elmer DTA-1700 with a heating rate 10 °C/min from30 °C to 800 °C. The samples were measured in a flow of air with a flow rate 40 ml/min.(4) UV-VisibleThe UV-visible experiments were preformed using Jesco Model 7850 UV/VISSpectrophotometer. Dry powder sample about 0.05 g was measured in a microslide.(5) FTIRThe sample was mixed with KBr powder with a ratio of 10:90. The IR spectra waspreformed on a Bio-Rad FTS- 45 Fourier Transform Infrared Spectrometer. The scane rangwas 400-4000 cm -1 .(6) Transmission Electron Microscopy (TEM)The sample powders were dissolved in water and became colloidal in the water. Thepowders in the colloidal solution was deposited on a grid with a holey carbon copper film andrapidly transferred to a Jeol TEM-1200 EX II electron microscope operating at 100 kV. TEMimages were recorded at magnification of 100000×, and some images were magnificated to apictures of 3 in × 5 in.(7) Scanning electron microscopy (SEM) and SEM-EDSScanning electron microscopy images were obtained with a Hitachi S-800 field emissionmicroscope using an acceleration voltage of 20 kV. Samples were placed on a stage especiallymade for SEM. Samples were coated with Pt prior to analysis and imaged directly. SEMimages were recorded at magnification of 5000 x to 10000 x. The magnification wascalibrated in pixel / nm on the camera. The chemical composition of the samples wasdetermined by scanning electron microscopy- X- ray energy dispersion spectrum (SEM-EDS)with accelerating voltage of 20 kV.(8) Ultravillet-Visible spectroscopy (UV-Vis)The diffuse reflectances UV-Vis were measured with a Cary 300 Bio UV-VisibleSpectrophotometer. Powder samples were loaded in a quartz cell with suprasil windows, andspectra were collected in the range from 300 nm to 800 nm against quartz standard.20

3.5 Photocatalyst reaction testing3.5.1 Ultra violet responsePhotocatalytic reactions were carried out in a continuous flow tank reactor. Thephotocatalyst powder (1g) was dispersed in a reactant solution (350 mL) in a down windowtype irradiation cell made of quartz reactor (500 ml). Sodium hydroxide aqueous solution wasemployed as an absorbent of carbon dioxide, and CO 2 was added continuously forphotoreduction of carbon dioxide into methanol. The light source was a 75 W halogen lamp(Ever bright). The amounts of methanol evolved were determined by gas chromatography(China Chromatography; GC-8900, propack-Q column, FID, He carrier).3.5.2 Visible light responsePhotocatalytic reactions were carried out in a continuous flow tank reactor. Thephotocatalyst powder (0.14 g) was dispersed in a reactant solution (50 mL) in a down windowtype irradiation cell made of Pyrex glass cell (75 ml). Potassium bicarbonate aqueoussolutions were employed as reactant solutions and carbon dioxide were added continuouslyfor CO 2 reduction into methanol. The light source was a 500 W halogen lamp (Ever bright;H-500). The amounts of methanol evolved were determined by gas chromatography (ChinaChromatography; GC-8900, propack-Q column, FID, He carrier).3.5.3 Analysis of productionCondition of GC:a. detector should be FID, the detection limit was about 5 ppm methanol.Injector: 120℃FID:150℃Oven:100℃b. carrier gas: 1.3 bar helium gas, about 30 cc/min.H2:0.45 bar,Air:1.2 bar,21

Na2O‧ 2SiO2‧nH2O +H2OmixingTi source(Titaniumisopropoxide)+ H2O2mixingC16TMABr+H2Omixingmixingadjust pH=10with 2M H2SO4hydrothermal inautoclave 100 o C,48hfilter with pure waterwashingdrying over nightcalcination540 o C ,6 hrTiMCM-41Figure 3.1. The flow chart of the synthesis of TiMCM-41.22

Figure 3.2 Teflon-lined stainless-steel autoclave.23

Chapter4. Results and Discussion4.1 Photoreduction under ultra-violet light with Ti-MCM-41Ti-MCM-41 with various Ti/Si ratio was synthesized. In synthesis procedure, make surethat the solution should be mixed well is an important key. Sodium silicate powder andquarternary ammonium respectively should be mixed well with water. The autoclave shouldbe quenched in ice water after synthesis. If the autoclave was cooled in room temperature, theproduct would separate into two parts, one was transparent gel and the other wasconglometerated, white solid with no characteristic XRD peak.4.1.1 XRDThe synthesized TiMCM-41 with various Si/Ti ratio were characterized by XRD. TheXRD pattern shows obviously diffraction peaks at d-spacing of 4.298, 2.424, 2.098,1.576, and1.198 nm, represent 100, 110, 200, 210,200 diffraction faces of hexagonal accumulativelattices (Figure 4.1).The XRD pattern shown in Figure 4.2 indicates the different intensity before and aftercalcination of 100-TiMCM-41. The intensity of diffraction peak after calcination is almosttwice than that before calcination. This result is similar with that of Marler et al.(1996). As ithas been reported, MCM-41 framework contracts upon calcination (Beck et al, 1992; Chen etal, 1993). In this work, the pore diameter after calcination is narrower than before calcination,the d-spacing of 100 diffraction peak decreases form 4.212 nm to 3.686 nm.Fig. 4-3 shows theXRD patterns of 50-TiMCM-41 with different synthetic time. The sample synthesized for 48h has a much higher crystallinity than that for 24 h one. Figures 4.4 and Figure 4.5 show thatthe crystallinity of peak d 100 was getting lower when titanium content increased. Thecrystallinity data in Figure 4.5 was calculated from d 100 peak intensities of pure siliciousMCM-41 and TiMCM-41 with various titanium contents. When Si/Ti molar ratio was up to25 (Figure 4.4C), the intensity of peak d 100 became very low, and it was difficult tosynthesize.4.1.2 N 2 SorptionThe measurement of the surface areas of the samples was achieved by BET(Brunauer-Emmett-Teller) method, and the pore size distribution was determined by BJH(Barrett-Joyner-Halenda) method.The N 2 isotherms and BJH pore plots of 100-TiMCM-41 and 25-TiMCM-41 are shownFigure 4.6 and Figure 4.7. The hysteresis loops of both are all categorized as Type H 1 , whichshows that adsorpion and desorpion are irreversible. The BJH calculation shows that porediameters are in a narrow rang between 2~3 nm. Since 25-TiMCM-41 has a lower crystallinity,its pore distribution was not as uniform as that of 100- TiMCM-41. The surface area ofTiMCM-41 decreased with titanium content, but did not make big difference on the mainpeak diameter (Table 4.1, Figure 4.8).24

Using d-spacing data from XRD patterns and pore diameter from N 2 sorption, the wallthickness is calculated. Figure 4.9 is the diagram of pore arrangement. Wall thickness can beobtained by a 0 - d, where a 0 is the unit cell parameter calculated from d spacing(a = 2 3 ), and d is main pore diameter. The results are shown in Table 4.2. The0d 100wall thickness is around 2.2nm, about the same order with pore diameter.4.1.3 DTA AnalysisThe DTA curves of 50-TiMCM-41 is shown in Figure 4.10. The desorption of H 2 O onthe surface occurs in the region of 50-130℃. The dissociation of surfactant used in synthesiswith a molecular bonding as an anion in the framework Si-O - , in the range of 300-380 ℃.The range of 380-540 ℃ was the dissociation of surfactant bonded with Ti-O - . There is noexothermic peak after 650 ℃, indicating the surfactant has been removed completely. Itshows that TiMCM-41 structure was quite stable between 650 to 880 ℃ .4.1.4 FTIRFigure 4.11 shows that the FTIR spectrum of 50-TiMCM-41 sample before calcinationhas two bands at 2700-2900 cm -1 . After calcination, the both peaks disappeared, whichindicates the organic template had been completely removed under the calcination condition.Figure 4.12 shows the FTIR spectra of pure silicious MCM-41 and 50-TiMCM-41. Theband at 960 cm -1 is clearly visible in both samples. For silicious MCM-41 this has beenassigned to the Si-O stretching vibrations of Si-O - R + groups. (Decottiguies et al.,1978). ForTi-contaig zeolites, such as TS-1, Ti-β, all have a band at 960 cm -1 , however, Boccuti et al,(1989) assigned it to Si-OH and Ti-O-Si bands. Therefore, this band may not be regarded as afirm proof for Ti incorporation.4.1.5 UV-visible SpectroscopyUV-visible technique has been used for characterization of the Ti 4+ ions in zeolites.Many researchers (Boccuti et al., 1989, Petrini et al., 1992, Camblor et al, 1992) had reportedthat signals at 220~270 nm could be attributed to be isolated Ti 4+ ion in an octahedralcoordination, with two water molecules in the metal coordination sphere. Figure 4.13 showsUV-visible spectra of various TiMCM-41 and TiO 2 . The band at 330 nm in the spectrum ofTiMCM-41 was absent and which can be obviously seen in the spectrum of TiO 2 . Thisindicates that titanium oxide was not present in significant amount in TiMCM-41. In addition,it shows that the intensity of the band shoulder increased with titanium content.4.1.6 TEMThe most detailed TEM investigation was published by Alfredsson et al.,(1994) forMCM-41 type materials. They reported that the pore channel is hexagonal rather than round,and some graphs showed equidistantly parallel bend, which was assumed as that thelamellar-to hexagonal phase transformation was not complete. Chenit et al.(1995) reported a25

different opinion about the equidistantly parallel bend. They reported that the equidistantlyparallel bend was not another “ lamellar phase”, but another image with mostly parallelelectron beam. Figure 4.14 shows the supposed schematic model. Lamellar appearance isexpected for beam directions in the plane defined by perpendicular to one family of channelwalls and the length of tubules. The equidistance between darker regions is a 3 / 2, where ais the distance from tube center to tube center. Figure 4.15 shows the TEM image of50-TiMCM-41, equidistantly parallel bend can be clearly seen, and the pore diameter pluswall thickness is about 3.27 nm. It is similar to the result calculated from XRD and N 2sorption data.4.1.7 Photocatalytic reaction testingCO 2 reacting with water was carried out using UV as the light source. The activity ofcarbon dioxide reduction of 25Ti-MCM-41 samples is better than Ti/Y zeolite samples. Themaximum photocatalytic activity is obtained over 25Ti-MCM-41. The methanol productionrate of 25Ti-MCM-41 was 42 μmol/h g-cat, and the production of 10% Ti/Y zeolite was30μmol/h.gcat.26

Figure 4.1 XRD pattern of pure silicate MCM-41.Figure 4.2 XRD patterns of 100-TiMCM-41. (A)After calcination, (B) Before calcination.27

Figure 4.3 XRD patterns of 50-TiMCM-41. (A)Synthesis 24 h, (B)Synthesis 48 h.Figure 4.4 XRD patterns of different TiMCM-41. (A)100-TiMCM-41, (B)50-TiMCM-41, (C)25-TiMCM-41.28

10080Cristalinity (%)60402000 1 2 3 4 5 6TiO 2 (%)Figure 4.5 Crystalinity of TiMCM-41.600.0Volume Adsorbed cm 3 /g STP500.0400.0300.0200.0100.0Col 15 vs Col 16Col 17 vs Col 18dV / dD10 100 1000Pore Diameter (A)0.00.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0Relative Pressure (P/P 0 )Figure 4.6 25-TiMCM-41 Isothermal Plot29

350Volume Adsorbed cm 3 /g STP30025020015010050Col 9 vs Col 10Col 11 vs Col 12dV/dD00.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0Reletive Pressure (P/P 0 )10 100 1000Pore Diameter (A)Figure 4.7 75-TiMCM-41 IsothermPlot.Table 4.1 N 2 Sorption Data of TiMCM-41.MCM-41(pure Silicon)TiMCM-41(Ti/Si:1/100)TiMCM-41(Ti/Si:1/25)TiMCM-41(Ti/Si:1/56)BET Area( m 2 / g )LangmuirArea( m 2 / g )Pore Volume(cm 3 / g)658 921 1.39 27588 848 0.58 22320 449 0.83 22473 608 0.65 28PeakDiameter( A)Ο30

BET Surface Area ( m 2 /g)60040020000.00 0.01 0.02 0.03 0.04 0.05Ti/Si Mole RatioFigure 4.8 BET Surface Area v. s. Ti/Si Mole Ratio.d 100 = spacingd = pore diameterw = wall thickenssFigure 4.9 Pore arrangement diagram, Marler et al., 1996.31

Table 4.2 Wall thickness of TiMCM-41.d 100 (nm) * d (nm) ** w (nm) ***pure silicate MCM-41 3.93 2.2 2.375-TiMCM-41 4.49 2.8 2.456-TiMCM-41 3.69 2.2 2.125-TiMCM-41 4.29 2.7 2.3* d 100 spacing**pore diameterwall thickenssFigure 4.10 DTA plot of 50-TiMCM-41.32

Figure 4.11 FTIR Spectra of TiMCM-41 (A) After calcination, (B) Before calcination.Figure 4.12 FTIR spectra of (A) silicious MCM-41, (B) 50-TiMCM-41.33

2.01.6MCM-4125-TiMCM-4175-TiMCM-41TiO2absorbance (a.u)1.20.80.40.0200 250 300 350 400Wavelength (nm)Figure 4.13 UV-vis spectra of various TiMCM-41 and TiO 2 .Figure 4.14 Schematic model showing apparent "lamellar structure" from a projection of ahexagonal array tubules, (Chenit, et al., 1995).34

Figure 4.15 TEM image of 50-TiMCM-41 (30000x)35

4.2 Photoreduction under visible light with InVO 4InVO4 photocatalysts were prepared with various preparation variables, including: (1)loading me tal, NiO, (2) different amount of NiO loading (0.5 wt%, and 1.0 wt%), (3)reduction-oxidation pretreatment.4.2.1 Effect of various amount of NiO loadingThe aqueous solution of nickel nitrate hexahydrate was added respectively into thesurface of the InVO4 powders. Water of the suspension was evaporated by a water bath understirring. Following, the dried powder was calcined at 350 O C for 1 hr in air using a mufflefurnace.4.2.1.1 XRDFigure 4.16 shows the XRD patterns of the as-prepared InVO 4 with various loadingmetal. The XRD patterns of InVO 4 samples prepared by solid reaction at 1123K wellconsisted with orthorhombic InVO 4-III phase spectrum, space group Cmcm, indicated that thesamples were fully crystallized InVO 4 (Figure 4.1A). The crystal lattice parameters wererefined as follows: a=5.7531(1) Å, b=8.5201(1) Å and c=6.5781(2) Å. The indexed result is ingood agreement with that reported in the JCPDS database card (No. 48-0898).Ye et al. (2002) has reported the structural of InVO 4 . The InVO 4 compound belongs tothe orthorhombic system, space group Cmcm, a = 5.7542(1), b= 8.5229(1) and c= 6. 5797(1)Å. The structure is com posed of two kinds of polyhedra: InO 6 octahedron and VO 4tetrahedron. The InO 6 octahedron connects to each other by sharing edge to form chains along[0 0 1] direction, which were linked together by the VO 4 tetrahedra. The band structure ofoxides is generally defined by d-level and O 2p-level, as confirmed by the theoreticalcalculations based on the first principles method for TiO 2 and InMO 4 (M= V, Nb, and Ta)photocatalysts (Lee et al., 2000). Figure 4.1B is a pattern of InVO 4 samples loaded NiO, oneaddition XRD peak appeared near 55.861 o (0 0 4) (Touboul et al., 1995), which might becausethe crystalline distortion induced by NiO loadings.4.2.1.2 SEMFigure 4.17 shows the SEM photographs of the InVO 4 samples prepared with variousloading amount of nickel. Figure 4.17A is a micrograph of InVO 4 samples, the particlediameters of InVO 4 samples were less than 6μm. The particles agglomerated in irregularshape with ca. 3~6 μm. Figure 4.17B is a micrograph of InVO 4 samples loaded with 0.5 wt%NiO on the catalysts, many pellets and pin-holes were observed on NiO/InVO 4 particles.Figure 4.17C is a micrograph of InVO 4 samples loaded with 1.0 wt% NiO on the catalysts,many pellets and pin-holes were observed on NiO/InVO 4 particles. It should be noted thatsuch Ni particles were not so homogeneously dispersed over InVO 4 support. However, it isdifficult to infer from a SEM photograph whether the Ni particles are located at the surface orbetween layers. The SEM-EDS results of InVO 4 prepared with various amount of NiO36

loading were given in Figure 4.19, and Figure 4.20. The nominal and actual amount ofloaded-NiO on InVO 4 samples are showed in Table 4.3.Figure 4.19 showed that nickel is present on the surface of 0.5 wt% NiO/InVO 4catalysts. These results also indicate that the InVO 4 phases are most probably well dispersed.No other contaminants were found. Therefore, the SEM-EDS result of supported Ni catalystsshowed that small nickel particles appeared to be embedded. Figure 4.20 showed that nickel ispresent on the surface of 1.0 wt% NiO/InVO 4 catalysts. These results also indicate that theInVO 4 phases are most probably well dispersed. No other contaminants were found.Therefore, the SEM-EDS result of supported Ni catalysts showed that small nickel particlesappeared to be embedded.4.2.1. 3 UV-VisFigure 4.21 shows the diffuse reflectance spectra of InVO 4 samples prepared withvarious loading amount of nickel. The InVO 4 compound showed obvious absorption in visiblelight region up to 704 nm. The band gap of InVO 4 was estimated to be about 1.8 eV from theonset of the absorption spectra (Figure 4.21A). For 0.5 wt% NiO/InVO 4 aftercalcination(Figure 4.21B), it showed obvious absorption in visible light region up to ca. 760nm. For 1.0 wt% NiO/InVO 4 after calcinations (Figure 4.21C), a broad and weak band at ca.745 nm was observed corresponding to octahedral Ni 2+ , as in NiO (Woo and Sohn, 2003;Houalla et al., 1982).4.2.1.4 Photocatalytic reaction testingThe activity of carbon dioxide reduction of InVO 4 samples prepared with variousloading amount of nickel and the band gap of catalysts are showed in Table 4.4. All catalystsproduce methanol from the photoreduction of CO 2 . All catalysts shows extremely higheractivities for carbon dioxide reduction under visble light irradiation(Figure 4.22). Themethanol yield of InVO 4 is 1.253μmole/gcath, and 1.0wt% NiO/InVO 4 gave the highest yieldof methanol is 1.71 μmole/gcat.h. The results showed that InVO 4 and NiO/InVO 4 withvarious amount of Ni are very active to carbon dioxide reduction (the incident light powerprobed near reactor was about 143 μW/cm 2 for λ= 300-900 nm, see Figure 4.18).37

Intensity (arb. units)CB0 10 20 30 40 50 60 70 80 90 1002θ (degree)AFigure 4.16 The XRD patterns of InVO 4 prepared with various amount of NiO loading. (A)InVO 4 , (B) 0.5wt% NiO/InVO 4 , (C) 1.0wt% NiO/InVO 4.38

(A) InVO 4(B) 0.5 wt% NiO/InVO 4Figure 4.17 The SEM micrographs of InVO4 prepared with various amount of NiO loading.(A) InVO 4 , (B) 0.5 wt% NiO/InVO 4 , (C) 1.0 wt% NiO/InVO 4 .39

(C) 1.0 wt% NiO/InVO 4Figure 4.17 The SEM micrographs of InVO4 prepared with various amount of NiO loading.(A) InVO 4 , (B) 0.5 wt% NiO/InVO 4 , (C) 1.0 wt% NiO/InVO 4 .35003000Current (mW/cm 2 )250020001500100050000 200 400 600 800 1000Wavelength (nm)Figure 4.18 The wavelength-current spectra of 500W halogen lamp, incident light powerprobed near reactor was about 143 μW/cm 2 for λ is from 300 to 900 nm.40

Figure 4.19 The SEM-EDS spectra of InVO 4 loaded with 0.5 wt% NiO.Figure 4.20 The SEM-EDS spectra of InVO 4 loaded with 1.0 wt% NiO.41

Table 4.3 The nominal and actual loading of NiO on InVO 4 samples.PhotocatalystsNominal NiO loadingon InVO 4 (wt%)Actual NiO loadingon InVO 4 (wt%)0.5 wt%NiO/InVO 40.5 3.201.0 wt%NiO/InVO 41.0 3.71Absorbance (arb. units)CB100 200 300 400 500 600 700 800 900Wavelength (nm)AFigure 4.21 The UV-Vis spectrum of InVO 4 prepared with various amount of NiO loading. (A)InVO 4 , (B) 0.5 wt% NiO/InVO 4 , (C) 1.0 wt% NiO/InVO 4 .42

2.0Methanol yield (μmol g -1 h -1 )1.61.20.80.40.0-0.5 0.0 0.5 1.0 1.5Amount of NiO loading (wt%)Figure 4.22 Dependence of the photocatalytic activity for carbon dioxide over NiO/InVO 4upon the amount of NiO loading; under visible light irradiation. Catalyst: 0.14g; 0.2N KHCO 3aqueous solution; 50ml.Table 4.4 Band gap of InVO4 seriousPhotocatalystsEg(eV)InVO 4 1.80.5wt% NiO/InVO 4 1.61.0wt% NiO/InVO 4 1.743

4.2.2 Effect of reduction-oxidation pretreatmentThe aqueous solution of nickel nitrate hexahydrate was added into the surface of theInVO 4 powders. Water of the suspension was evaporated by a water bath under stirring.Following, the dried powder was calcined at 350 O C for 1 hr in air using a muffle furnace,respectively. The photocatalysts were prepared by H 2 (pressure: 0.3 M Pa, flow rate: 25cc/min) reduction at 500°C for 2 h and subsequent O 2 (pressure: 0.15 M Pa, flow rate: 25cc/min) oxidation at 200°C for 1 h. The pretreatment method had a great effect on the activityof the catalyst.4.2.2.1 XRDFigure 4.23 shows the XRD patterns of the InVO 4 samples synthesized withpretreatment on various amount of nickel. The XRD patterns of InVO 4 samples prepared bysolid reaction at 1123K well consisted with orthorhombic InVO 4 -III phase spectrum, spacegroup Cmcm, indicated that the samples were fully crystallized orthorhombic InVO 4 (Figure4.27A). The crystal lattice parameters were refined as follows: a=5.7531(1) Å, b=8.5201(1) Åand c=6.5781(2) Å. The indexed result is in good agreement with that reported in the JCPDSdatabase card (No. 48-0898).Figure 4.23B revealed that peaks corresponding to Ni species such as Ni or NiO werehardly observed in the pattern of 0.5 wt% NiO/InVO 4 R500-O200, suggesting nocharacteristic peaks of Ni species were observed for powder X-ray diffraction indicating thatno extensive formation of No species on the InVO 4 surface and the size of Ni species onInVO 4 is too small to have a sharp peak because of line broadening. After pretreatment on 0.5wt% NiO/InVO 4 , showed the peak of XRD pattern apparent decreased. Therefore, thecrystalline of 0.5 wt% NiO/InVO 4 R500-O200 became weaker than without pretreatment.Figure 4.23C is a pattern of InVO 4 samples with pretreatment on loaded 1.0 wt% NiO,suggesting no extensive formation of Ni species on the InVO 4 surface and the size of Nispecies on InVO 4 is t oo small to have a sharp peak because of line broadening. Afterpretreatment on 1 wt% NiO/InVO 4 , showed the intensity of XRD pattern apparent decreased.Therefore, the crystalline of 1 wt% NiO/InVO 4 R500-O200 became weaker than withoutpretreatment.4.2.2.2 SEMFigure 4.24 shows the SEM photographs of the InVO 4 samples prepared withpretreatment on various loading amount of nickel. Figure 4.24A is a micrograph of InVO 4samples, the particle diameters of InVO 4 samples were less than 6μm. The particlesagglomerated in irregular shape with ca. 3~6 μm. Figure 4.24B is a micrograph of InVO 4samples loaded with 0.5 wt% NiO and pretreatment on the catalysts, many pellets wereobserved on NiO/InVO 4 R500-O200 particles. Figure 4.24C is a micrograph of InVO 4samples loaded with 1.0 wt% NiO and pretreatment on the catalysts, many pellets and44

pin-holes were observed on NiO/InVO 4 R500-O200 particles. It should be noted that such Niparticles were not so homogeneously dispersed over InVO 4 support. However, it is difficult toinfer from a SEM photograph whether the Ni particles are located at the surface or betweenlayers.4.2.2.3 UV-VisFigure 4.25 shows the diffuse reflectance spectra of InVO 4 samples prepared withpretreatment on various loading amount of nicke. The InVO 4 compound showed obviousabsorption in visible light region up to 704 nm. The band gap of InVO 4 was estimated to beabout 1.8 eV from the onset of the absorption spectra (Table 4.4). For 0.5 wt% NiO/InVO 4after pretreatment, it showed obvious absorption in visible light region up to ca. 760 nm(Figure 4.25B). After pretreatment on 1.0 wt% NiO/InVO 4 after pretreatment, a broad andweak band at ca. 745 nm was observed corresponding to octahedral Ni 2+ , as in NiO (Woo andSohn, 2003; Houalla et al., 1982) (Figure 4.25C).4.2.2.4 Photocatalytic reaction testingThe activity of carbon dioxide reduction of as-prepared InVO 4 samples treated undervarious loading metal conditions with pretreatment and the band gap of catalysts are showedin Table 4.5. All catalysts produce methanol from the photoreduction of carbon dioxide. Theresults showed that InVO 4 and NiO/InVO 4 with pretreatment on various amount of Ni arevery active to carbon dioxide reduction (the incident light power probed near reactor wasabout 143 μW/cm 2 for λ= 300-900 nm, see Figure 4.18). All catalysts shows extremely higheractivities for CO 2 reduction compared to the activity of NiO x /InVO 4.Figure 4.26 shows the dependence of the photocatalytic activity for CO 2 reduction overNiO/InVO 4 upon the amount of NiO loaded with pretreatment. When the catalyst was loadedwith 0.5 wt% of Ni and via pretreatment, the activity reached a maximum, and furtherNi-loading led to saturation of activity. The number of photons absorbed into the InVO 4particles became attenuated at large amounts of Ni-loading, which was probably the cause ofthe saturation of activity.The pretreatment method had a great effect on the activity of the catalyst. Themaximum photocatalytic activity is obtained over 0.5 wt% NiO/InVO 4 with reduced at 500for 2 h and oxidized at 200 ◦C for 1 h. The methanol production rate of 0.5 wt% NiO/InVO 4was 2.279 μmol/h g-cat. The improved activity of NiO/InVO 4 might attribute to thedistribution of photogenerated electrons by loading NiO and the extensive active kinksoffered by the pin-holes on NiO/InVO 4 particles.45

Intensity (arb. units)CB0 10 20 30 40 50 60 70 80 90 1002θ (degree)AFigure 4.23 The XRD patterns of InVO 4 prepared with pretreatment on various amount ofNiO loading. (A) InVO 4 , (B) 0.5wt% NiO/InVO 4 R500-O200, (C) 1.0wt% NiO/InVO 4R500-O200 .46

(A) InVO 4(B) 0.5 wt% NiO/InVO 4 R500-O200Figure 4.24 The SEM micrographs of InVO 4 prepared with pretreatment on various amount ofNiO loading. (A) InVO 4 , (B) 0.5 wt% NiO/InVO 4 R500-O200, (C) 1.0 wt% NiO/InVO 4R500-O200.47

(C) 1.0 wt% NiO/InVO 4 R500-O200Figure 4.24 The SEM micrographs of InVO 4 prepared with pretreatment on various amount ofNiO loading. (A) InVO 4 , (B) 0.5 wt% NiO/InVO 4 R500-O200, (C) 1.0 wt% NiO/InVO 4R500-O200.48

Absorbance (arb. units)EDA100 200 300 400 500 600 700 800 900Wavelength (nm)Figure 4.25 The UV-Vis spectra of InVO 4 prepared with pretreatment on various amount ofNiO loading. (A) InVO 4 , (B) 0.5 wt% NiO/InVO 4 R500-O200, (C) 1.0 wt% NiO/InVO 4R500-O200.Table 4.5 Band gap of InVO4 serious with pretreatmentPhotocatalystsEg(eV)InVO 4 1.80.5wt% NiO/InVO 4R500-O2001.0wt% NiO/InVO 4R500-O2001.61.749

2.4Methanol yield (μmol g -1 h -1 )2.01.61.20.80.40.0-0.5 0.0 0.5 1.0 1.5Amount of NiO loading (wt%)Figure 4.26 Dependence of the photocatalytic activity for carbon dioxide over NiO/InVO 4upon the amount of NiO loading; under visible light irradiation. Catalyst: 0.14g; 0.2N KHCO 3aqueous solution; 50ml.50

Chapter5. ConclusionFor UV light test, a series of Ti/HY zeolite and Ti-MCM-41 with various Ti contents havebeen synthesized successfully. The catalysts were characterized by various techniques. Theresults showed that Ti was in tetrahedral site which was believed to be the active sites formethanol synthesis from carbon dioxide by photocatalysis. The preliminary reaction testingshowed that the catalysts are active for this reaction.The photocatalytic reaction was carrierout in a quartz cell with a 75W metal halogen light, the rate of 10wt% Ti/HY catalysts forCO 2 reduction to produce methanol is 30μmol/h g-cat Ti, and the rate of 25Ti-MCM-41 isreached 42μmol/h g-cat Ti.For visible light test, a serious of InVO 4 were fully crystallized by characterized bypowder X-ray diffraction (XRD). It was seen that many pin-holes appeared on InVO 4 afterloading NiO,and it help reactive activity. The pretreatment method had a great effect on theactivity of the catalyst. 0.5wt% NiO/InVO 4 with pretreatment gave the highest yield ofmethanol, 2.279 μmol/h g-cat.51

Chapter6. ReferencesAlfredsson, V.; Keung, M.; Monnier, A.; Stuky , G. D.; Unger, K. K.; Schuth, F."High-Resolution Transmission Electron-Microscopy of Mesoporous MCM-41", J.Chem. Soc. Chem. Commun. 1994, 921-922Anpo, M., H. Yamashita, Y. Ichihashi, Y. Fujii, M. Honda, Photocatalytic Reduction of CO 2with H 2 O on Titaniun Oxide Anchored within Micropores of Zeolite: Effect of theStructure of the Active Sites and the Addition of Pt, J. Phys. Chem. B 1997, 101,2632-2636.Anpo, M., H. Yamashita, K. Ikeue, Y. Fujii, S. G. Zhang, Y. Ichihashi, D. R. Park, Y. Suzuki,K. Koyano, T. Tatsumi, Photocatalytic Reduction of CO 2 with H 2 O on Ti-MCM-41 andTi-MCM-48 Mesoporous Zeolite Catalysys, Catal. Today 44 (1998) 327-332.Beck, J. S.; Vartuli, J. C.; Roth, W. J.; Leonowicz, M. E.; Kresge, C. T.; Schmitt, K. D.;Higgins, J. B.; Schlenker, J. L. "A new Family of Mesoporous Molecular SievesPrepared with Liquid Crystal Temples", J. Am. Chem. Soc. 1992, 114, 10834Blasco, T.; Camblor, M. A.; Corma, A.; Perez-Pariente, J. "The state of Ti inTitanoaluminosilicates Isomirphous with Zeolite-Beta", J. Am. Chem. Soc. 1993, 115,11806-11813.Boccuti, M.; Rao, K. M.; Zeccchina, A.; Leofanti, G.; Petrini, G. Stud. Surf. Sci. Catal. 1989,48, 133Camblor, M. A.; Corma, A.; Perez-Pariente, J. "Synthesis of TitanoaluminosilicatesIsomorphous to Zeolite Beta", Active as Oxidation Catalysts. Zeolites. 1993, 13, 82Chen, C. Y.; Burkett, S. L.; Lin, H. X.; Davis, M. E. "Studies on Mesoporous Materials II.Synthesis Mechanism of MCM-41", Microporous Mater. 1993, 2, 27-34Chenite, A.; Y. Le Page, Sayari, A." Direct TEM Imaging of Tubules in Calcined MCM-41Type Mesoporous Materials ", Chem Mater. 1995, 7, 1015-1019Corma, A; Navarro, M. T.; Pariente, J. P. Chem. Soc., Chem. Commun. 1994(a), 147.Corma, A.; Camblor, M. A.;Esteve, P.; Martinez, A.; Perez-Pariente, J. "Activity of Ti-BetaCatalyst for The Seletive Oxidation of Alkenes and Alkanes", J. Catal. 1994(b),151-158Corma, A.; Navarro, M. T.; Perez-Pariente, J. "Synthesis of an Ultralarge Pore TitaniumSilicate for Selective Oxidation of Hydrocarbons", J. Chem. Soc. Chem. Commun.1994(c), 147-148Corma, A.; Navarro, M. T.; Perez-Pariente, J.; Sanchez, F. "Preparation and Properties ofTi-Containing MCM-41", Stud. Surf. Sci. Catal. 1994(d), 84, 69-75Camblor, M. A.; Corma, A.; Martinez, A. "Synthesis of Titaniumsilico-aluminateIsomorphous to Zeolite-Beta and Its Applications as a Catalyst for the SelectivityOxidation of Large Organic-Molecules", J. Chem. Soc., Chem. Commun. 1992,52

589-590Decittiguies. M.; Phalippou, J.; Zarzycki, J. J. Mater. Sci. 1978, 13, 2605Firouzi, A.; Monnier, A.; Bull, L. M.; Besier, T.; Sieger, P.; Huo, Q.; Walker, S. A.;Zasadzinski, J. A.; Glinka, C.; Nicol, J.; Margoles, D.; Stucky, G. D.; Chemlka, B.F."Cooperative Organization of Inorganic-Surfactant and Biomimetic Assemblies”,Science, 1995, 267, 1138-1143Gontier, S.; Tuel, A. "Synthesis and Characterization of Ti-Containing Mesoporous Silicates",Zeolites. 1995, 601-610Hue, Q. S. ; Margolese, D. I.; Cilesla, U.; Feng, P.; Gier, T. E.; Sieger, P.; Leon, R.; Petroff,P.M.; Schuth, F.; Stucky, G.D. "Generalized Synthesis of Periodic Surfactant InorganicComposite-Materials", Nature 1994(a), 368, 317-321Huo, Q. S.; Margolese, D. I.; Cilesla, U.; Demuth, D. G.; Feng, P.; Gier, T. E.; Sieger, P.;Firouzi, A.; Chmelka, B.F.; Schuth, F.; Stucky, G.D. "Organization ofOrganic-Molecules with Inorganic Molecular-Species into Nanocomposite BiphasesArray", Chem. Mater. 1994(b), 6, 1176-1191.Huo, Q.; David, I. M.; Galen, D. S. Chem. Master. 1996, 8, 1147-1160Vartul i, J. C.; Schmitt, K. D.; Kresge, C. T.; Roth, W. J.; Leonowicz, M. E.; McCullen, S. B.;Hellring, S. D.; Beck, J. S.; Schlenker, J. L. Olson, D. H.; Sheppard, E. W. "Synthesisof Mesoporous Materials-Liquid-Crystal Templating Versus Intercalation of LayeredSilicates", Chem. Mater. 1994, 6, 2070-22077.Ikeue, K., H. Yamashita, M. Anpo, Photocatalytic Reduction of CO 2 with H 2 O on TitaniumOxide Prepared within the FSM-16 Mesoporous Zeolite, Chem. Lett. 1999 1135-1136.Ikeue, K., H. Yamashita, M. Anpo, Photocatalytic Reduction of CO 2 with H 2 O on Ti-β ZeolitePhotocatalysts: Effect of the Hydrophobic and Hydrophilic Properties, J. Phys. Chem.B 2001, 105, 8350-8355.Ikeue, K., H. Mukai, H. Yamashita, S. Inagaki, M. Matsuoka, M. Anpo, Characterization andPhotocatalytic Reduction of CO 2 with H 2 O on Ti/FSM-16 Synthesized by VariousPreparation Methods, J. Synchrotron Rad. (2001) 8, 640-642.Ikeue, K., S. Nozaki, M. Ogawa, M. Anpo, Characterization of Self-Standing Ti-ContainingPorous Silica Thin Film and Their Reactivity for the photocatalytic Reduction of Cwith H 2 O, Catal. Today 74 (2002) 241-248.Ikeue, K., S. Nozaki, M. Ogawa, M. Anpo, Photocatalytic Reduction of CO 2 with H 2 O onTi-containing Porous Silica Thin Film Pfotocatalysts, Catal. Lett. Vol. 80, No. 3-4, June2002, 111-114.Israelachvili, J.N.; Mitchell, D. J.; Ninham, B.W. J. Chem. Soc., Faraday Trans. II, 1976, 72,1527Kresge, C. T.; Leonowicz, M. E.; Roth., W. J.; Vartuli, J. C.; Beck, J. S. "OrderedO 253

Mesoporous Molecular-Sieves Snthesized by a Liquid-Crystal Template Mechanism",Nature. 1992, 359, 710-712.Koyano, K. A.; Tatsumi, T. "Synthesis of Titanium-Containing MCM-41", MicroporousMater., 1997, 10, 259-271Lin, H. P.; Mou, C. Y. "Tubeles-within-A-Tuble Hierarchial order of MesoporousMolecular-Sieves in MCM-41", Science, 1996, 273, 765-768Marler, B.; Oberhagemann, U.; Vortmann, S.; Gies, H. Microporous Mater. 1996, 6, 375Monn ier, A.; Fchuth, Q.; Huo, Q.; Kumar, D.; Margoleses, R. S.; Maxwell, G. D.; Stucky, M.;Krishnamutry, P.; Petroff, A.; Firouzi, M.; Janicke, D.; Chmelka, B. F., Science. 1993,261. 1299Petrin i, G.; Cesana, A.; De Alberti, G.; Giamello, E.; Leofanti, G.; Padovan, M.; Paparatto, G.;Rofia, P. Stud. Surf. Sci. Catal. 1991, 68, 761.Sayari, A., "Catalysis by Crystalline Mesoporous Molecular Sieves", Chem. Mater. 1996, 8,1840-1852Tanev, P. T.; Chibwe, M.; Pinnavaia, T. J. "Titanium-Containing MesoporousMolecular-Sieves for Catalytic-Oxidation of Aromatic-Compounds", Nature, 1994, 368,321-323Reddy, J. S.; Kumar, R.; Ratnasamy, P., Appl. Catal. 1990, L1, 58.Rhee, C. H.; Lee, J. S. "Thermal and Chemical-Stability of Titanium-Substituted Mcm-41",Catal. Lett. 1996, 40, 261-264Ryoo, R.; Kin, J. M.; Ko, C. H., "Disordered Molecular-Sieve with Branched MesoporousChannel Network", J. Phys. Chem. 1996, 100, 17718-17721.Shioya, Y., K. Ikeue, M. Ogawa, M. Anpo, “Synthesis of Transparent Ti-containingMesoporous Silica Thin Film Materials and Their Unique Photocatalytic Activity forthe Reduction of CO 2 with H 2 O”, Appl. Catal., A: General 254 (2003) 251-259.Thangaraj, A.; Kumar, R.; Mirajkar, S. P; Ratnasamy, P., "Catalytic Properties of CrystallineTitanium Silicalites. 1. Synthesis and Characterization of Titanium-Rich Zelites withMFI Structure", J. Catal. 1991, 130, 1-8Vartuli, J. C.; Schmitt, K.D.; Kresge, C. T.; Roth, W. J.; Leonowicz, M. E.; McCullen, S. B.;Hellring, S. D.; Beck, J. S.; Schlenker, J. L. Olson, D. H.; Sheppard, E. W."Development of a Formation Mechanism for M41S Materials", Stud. Surf. Sci. Catal.1994, 84, 53.Yama shita, H., Y. Fujii, Y. Ichihashi, S. G. Zhang, K. Ikeue, D. R. Park, K. Koyano, T. Tatsumi,M. Anpo, Selective Formation of CH 3 OH in the Photocatalytic Reduction of CO 2 withH 2 O on Titantium Oxide Highly dispersed within Zeolites and Mesoporous MolecularSieves, Catal. Today 45 (1998) 221-227.54

群 體 計 畫 之 整 合 成 果二 氧 化 碳 是 導 致 全 球 暖 化 ( Global Warming) 主 要 因 素 之 一 , 雖 然 自 然 界 生 物 的 活 動會 排 放 二 氧 化 碳 , 碳 元 素 的 轉 換 與 循 環 , 使 得 大 氣 中 二 氧 化 碳 的 濃 度 一 直 維 持 在 平 衡 的狀 態 , 但 最 近 數 十 年 來 , 因 為 大 量 化 石 燃 料 的 使 用 結 果 , 僅 靠 植 物 的 光 合 作 用 與 其 他 轉換 機 制 , 無 法 消 化 化 石 燃 料 燃 燒 所 產 生 之 大 量 二 氧 化 碳 ( 談 駿 嵩 ,2003)。 相 對 於 全 球 人口 的 增 加 , 全 球 能 源 需 求 也 跟 著 增 加 , 由 於 目 前 之 能 源 供 應 仍 有 將 近 85% 為 化 石 燃 料 ,短 期 內 極 難 有 巨 幅 改 變 , 因 此 二 氧 化 碳 的 排 放 量 勢 必 隨 著 增 加 。 為 降 低 未 來 因 溫 室 氣 體減 量 對 我 國 產 業 造 成 之 影 響 必 須 及 早 對 研 發 新 技 術 將 溫 室 氣 體 ( 特 別 是 CO 2 ) 等 進 行 減 量之 措 施 。 我 國 工 業 所 排 放 之 CO 2 約 佔 全 國 CO 2 總 排 放 量 之 50 ~ 55%, 其 中 又 以 鋼 鐵 、 石化 、 水 泥 、 紡 織 及 造 紙 等 產 業 排 放 量 最 大 , 由 於 這 些 產 業 均 為 基 礎 產 業 , 且 與 其 他 產 業之 關 連 性 相 當 大 , 不 能 因 為 需 要 降 低 CO 2 的 排 放 量 而 限 制 各 產 業 之 發 展 , 因 此 如 何 以 最新 的 技 術 發 展 來 回 收 CO 2 以 形 成 新 資 源 成 為 相 當 重 要 的 考 慮 因 素 。 為 有 效 降 低 大 氣 層 中CO 2 濃 度 , 並 進 而 加 以 循 環 利 用 , 目 前 已 發 展 出 數 種 可 行 的 處 理 技 術 , 有 物 理 儲 置 法(physi cal storage)、 化 學 固 定 法 (chemical fixation)、 生 物 固 定 法 (biological fixation) 等 ,而 化 學 固 定 法 中 之 光 化 學 固 定 法 是 一 富 有 潛 力 之 可 行 方 法 。 一 般 處 理 煙 道 氣 中 二 氧 化 碳主 要 的 方 法 大 致 有 化 學 溶 劑 吸 收 法 、 低 溫 冷 凝 法 、 薄 膜 分 離 法 、 物 理 吸 收 法 、 物 理 吸 附法 等 。 目 前 常 用 的 處 理 方 式 主 要 以 化 學 溶 劑 吸 收 法 為 主 , 但 由 於 採 用 化 學 溶 劑 吸 收 法時 , 不 但 其 處 理 率 不 彰 , 且 會 產 生 廢 水 污 染 的 問 題 , 因 此 如 何 回 收 二 氧 化 碳 並 以 再 利 用已 成 為 目 前 發 展 的 新 趨 勢 。總 計 劃 「 溫 室 氣 體 之 回 收 利 用 及 技 術 研 究 」 之 目 的 , 在 於 將 二 氧 化 碳 回 收 並 且 利 用回 收 的 二 氧 化 碳 講 期 轉 化 成 為 興 新 能 源 , 以 減 低 能 源 的 浪 費 。 子 計 畫 三 主 持 人 大 同 大 學陳 嘉 明 教 授 嘗 試 以 先 進 技 術 分 餾 器 ( 即 為 一 種 進 階 多 模 組 的 變 壓 吸 附 裝 置 ) 測 試 其 分 離 濃縮 二 氧 化 碳 的 效 率 , 嘗 試 改 變 不 同 的 操 作 條 件 , 以 達 到 分 離 濃 縮 二 氧 化 碳 之 目 的 。 總 計55

劃 暨 子 計 劃 一 主 持 人 中 央 大 學 陳 郁 文 教 授 以 及 子 計 畫 二 主 持 人 台 灣 大 學 張 慶 源 教 授 皆是 利 用 奈 米 光 觸 媒 將 二 氧 化 碳 反 應 , 分 別 生 成 甲 醇 及 乙 烯 。由 於 溫 室 效 應 的 影 響 , 工 業 大 量 排 放 的 二 氧 化 碳 之 減 量 一 直 是 目 前 各 方 面 所 關 心 的重 要 議 題 。 除 了 各 種 以 二 氧 化 碳 為 原 料 的 反 應 研 究 被 大 量 探 討 外 , 前 題 是 需 先 將 廢 氣 中的 二 氧 化 碳 分 離 與 濃 縮 出 來 , 才 能 用 以 作 為 反 應 原 料 。 本 子 計 畫 三 探 討 以 美 國SeQual公 司 發 展 出 來 的 一 種 特 殊 變 壓 吸 附 ( Pressure Swing Adsorption , 簡 稱 PSA) 裝 置 , 稱 為先 進 技 術 分 餾 器 ( Advanced Technology Fractionator, 簡 稱 ATF), 用 來 分 離 與 濃 縮 二 氧化 碳 的 可 行 性 。 ATF 的 特 點 是 使 用 12 個 床 體 以 及 旋 轉 閥 , 巧 妙 地 控 制 氣 流 的 通 路 , 使得 吸 附 與 脫 附 能 妥 善 配 合 , 整 個 裝 置 體 積 也 可 以 大 幅 縮 小 。 評 估 修 改 SeQual 的 ATF 模組 與 旋 轉 閥 控 制 , 嘗 試 改 變 不 同 的 操 作 條 件 ( 廢 氣 成 分 、 廢 氣 流 量 、 旋 轉 閥 轉 速 、 加 壓與 減 壓 循 環 等 ), 以 達 到 分 離 濃 縮 二 氧 化 碳 之 目 的 。另 外 子 計 劃 一 及 子 計 畫 二 利 用 奈 米 金 屬 光 觸 媒 還 原 CO 2 以 生 成 甲 醇 及 乙 烯 , 提 供 作為 工 業 上 之 原 料 。 一 方 面 可 以 降 低 溫 室 效 應 氣 體 排 放 , 另 一 方 面 可 以 增 加 石 化 資 源 的 產生 來 源 。 子 計 畫 一 的 目 的 在 於 以 紫 外 光 為 光 源 , 利 用 Ti/HY 與 Ti-MCM-41 觸 媒 將 二 氧 化碳 與 水 反 應 生 成 甲 醇 。 經 由 50 小 時 光 照 的 液 相 反 應 後 ,10% Ti/Y zeolite 可 產 生 30μmol/h.gcat.,25Ti-MCM-41 產 生 42 μmol/h.gcat. 為 最 佳 。子 計 畫 二 則 利 用 光 觸 媒 (Cu/TiO 2 、Ag/TiO 2 ), 經 由 波 長 254 nm 的 UV 燈 管 照 光 產 生 電子 與 電 洞 對 , 並 結 合 電 解 程 序 將 CO 2 還 原 成 甲 醇 以 及 乙 烯 。 共 使 用 四 種 不 同 還 原 程 序 ,方 法 與 結 果 分 別 為 : (1) Ag/TiO 2 光 催 化 還 原 氣 相 CO 2 程 序 : 產 物 為 甲 醇 , 反 應 24 小 時 後最 大 甲 醇 產 量 達 到 48.3 μg;(2) Ag/TiO 2 和 Cu/TiO 2 光 催 化 還 原 液 相 CO 2 程 序 : 反 應 產 物 亦以 甲 醇 為 主 , 結 果 顯 示 反 應 28 小 時 ,Ag/TiO 2 (124.46 μg) 催 化 效 果 較 Cu/TiO 2 (53.93 μg )為 佳 ;(3) 三 相 [ 氣 (CO 2 )/ 液 (NaCO 3 /CuCl 2 )/ 固 (Cu/TiO 2 )] 光 催 化 CO 2 還 原 程 序 : 在 溶 液 為 1 MCuCl 2 只 有 磁 石 攪 拌 下 甲 烷 產 率 最 高 , 反 應 28 小 時 後 系 統 之 甲 烷 產 量 可 達 122.6 μg;(4)三 相 [ 氣 (CO 2 )/ 液 (NaCO 3 /CuCl 2 )/ 固 (Cu/TiO 2 )] 光 催 化 結 合 紅 銅 電 極 電 解 法 來 還 原 CO 2 程序 : 此 方 法 在 碳 酸 鈉 添 加 0.1 M, 反 應 3 小 時 且 有 2wt. % Cu/TiO 2 觸 媒 下 ,CO 2 最 高 降 解率 可 達 89 %。 而 於 碳 酸 鈉 添 加 0.1 M, 反 應 3 小 時 且 無 Cu/TiO 2 觸 媒 下 , 乙 烯 產 量 最 高 ,56

可 達 37,062 μg, 選 擇 率 可 達 39.07%。子 計 畫 三 , 首 先 分 析 固 定 廢 氣 組 成 與 進 料 速 率 之 ATF 動 態 分 析 , 可 以 知 道 在 短 時 間內 二 氧 化 碳 之 出 口 端 即 可 達 到 穩 定 之 濃 度 , 顯 見 ATF 在 氣 體 出 口 濃 度 的 穩 定 性 上 較 傳 統之 雙 床 式 PSA 為 佳 。 且 二 氧 化 碳 出 口 與 入 口 體 積 濃 度 比 為 23%/9.1%, 有 初 步 之 濃 縮 分離 效 果 。 再 透 過 改 變 不 同 之 吸 附 與 脫 附 之 週 期 時 間 , 得 知 當 轉 速 變 小 時 表 示 每 一 組 管 柱之 吸 附 與 脫 附 之 週 期 均 變 長 , 系 統 有 較 充 裕 之 時 間 達 到 穩 定 的 吸 附 脫 附 效 果 , 所 以 反 應在 較 高 的 出 口 濃 度 上 。 再 以 相 同 進 料 濃 度 但 不 同 進 料 速 率 的 影 響 , 發 現 進 料 速 率 增 加 對分 離 的 效 果 也 會 增 加 , 而 回 收 的 比 值 則 頗 為 接 近 。將 對 於 子 計 畫 一 , 目 前 主 要 針 對 紫 外 光 範 圍 作 光 反 應 分 析 , 後 續 仍 需 針 對 產 率 與 轉化 率 之 提 升 做 更 進 一 步 之 研 究 , 例 如 針 對 光 照 方 向 對 反 應 器 做 修 改 , 或 是 改 變 溶 液 種 類及 濃 度 。 另 外 , 更 可 以 將 紫 外 光 光 源 變 更 為 可 見 光 光 源 , 並 選 用 可 見 光 觸 媒 , 讓 反 應 能在 可 見 光 下 進 行 。 因 太 陽 光 中 , 可 見 光 所 佔 的 比 例 高 達 百 分 之 四 十 三 , 若 將 來 能 充 分 利用 太 陽 能 當 作 光 源 , 將 可 以 達 到 節 省 能 源 , 對 環 境 影 響 達 到 零 污 染 , 並 減 少 二 氧 化 碳 的含 量 , 一 舉 多 得 。子 計 畫 二 , 嘗 試 了 四 種 方 法 , 在 不 同 操 作 條 件 下 , 結 果 顯 示 在 一 大 氣 壓 下 氣 相 和 液相 CO 2 還 原 反 應 主 要 產 物 為 甲 醇 。 第 二 種 方 法 為 液 相 曝 CO 2 反 應 , 主 要 產 物 為 甲 醇 。 而第 三 種 實 驗 方 法 條 件 下 , 於 Cu/TiO 2 水 溶 液 中 添 加 CuCl 2 之 結 果 顯 示 有 甲 烷 之 現 象 。 而 第四 種 方 法 之 結 果 產 物 有 甲 烷 、 乙 烯 、 一 氧 化 碳 、 氫 氣 等 , 此 程 序 亦 為 本 研 究 團 隊 首 先 提出 之 新 進 技 術 , 但 由 於 目 前 所 使 用 光 觸 媒 有 些 微 抑 制 甲 烷 和 乙 烯 的 生 成 , 因 此 未 來 本 研究 團 隊 之 主 要 研 究 方 向 為 尋 求 更 高 選 擇 率 及 更 有 效 之 觸 媒 , 增 進 乙 烯 產 量 、 選 擇 率 及 CO 2轉 化 率 。計 畫 三 已 初 步 驗 證 小 型 之 ATF 系 統 對 二 氧 化 碳 之 回 收 與 分 離 有 一 定 之 效 果 , 值 得 進一 步 研 究 與 開 發 。 仍 有 許 多 問 題 必 須 探 討 與 克 服 , 例 如 : 對 二 氧 化 碳 低 親 和 性 之 吸 附 劑尋 找 與 開 發 ; 提 昇 出 口 二 氧 化 碳 純 度 以 符 合 後 續 以 二 氧 化 碳 為 反 應 物 之 需 求 ( 詳 見 其 他57

子 計 畫 ); 系 統 放 大 設 計 之 研 究 與 探 討 ; 以 混 成 分 離 處 理 系 統 (Hybrid system) 處 理 二 氧 化碳 回 收 與 濃 縮 評 估 與 開 發 等 。58